1. Field of the Invention
The present invention relates to a process for producing octahydrocoumarins by reducing coumarins and/or dihydrocoumarins with hydrogen in the presence of an alcohol and a ruthenium catalyst, and optionally further heating the reaction mixture obtained by the reduction reaction. The present invention further relates to octahydrocoumarins produced as a result of that process. The octahydrocoumarins are important compounds in the perfume industry and are also useful as synthesis intermediates in the chemical industry.
2. Description of Related Art
As conventional processes for reducing coumarins and/or dihydrocoumarins to produce octahydrocoumarins, which are important compounds in the perfume and chemical industry, there has hitherto been known a process of reducing coumarin with hydrogen in a glacial acetic acid in the presence of a platinum oxide catalyst, e.g., Pharmaceutical Journal, 74, 895-898(1954), the disclosure of which is incorporated herein by reference, and a process of reducing coumarin with hydrogen in cycloheptane or ethanol in the presence of a Raney nickel or copper-chromite catalyst, e.g., J. Am. Chem. Soc., 62, 283-287(1940), the disclosure of which is also incorporated herein by reference.
However, the conventional processes mentioned above are not industrially satisfactory. Regarding the process of reducing coumarin with hydrogen in the presence of a platinum oxide catalyst, a large amount of expensive platinum oxide is used and the yield of octahydrocoumarin is not satisfactory. Regarding the process of reducing coumarin in the presence of a Raney nickel or copper-chromite catalyst, the reduction of coumarin is carried out under a hydrogen pressure between 100 and 200 atm and the yield of octahydrocoumarin is not satisfactory.